Mask holder



FIG. 1 is a front perspective view of a mask holder;

FIG. 2 is a front elevational view of the mask holder of FIG. 1;

FIG. 3 is a rear elevational view of the mask holder of FIG. 1;

FIG. 4 is a right side elevational view of the mask holder of FIG. 1;

FIG. 5 is a left side elevational view of the mask holder of FIG. 1;

FIG. 6 is a top elevational view of the mask holder of FIG. 1;

FIG. 7 is a bottom elevational view of the mask holder of FIG. 1; and,

FIG. 8 is a longitudinal cross sectional view of the mask holder of FIG. 1 taken along the plane 8-8 shown in FIG. 2.

The broken lines in the drawings illustrate portions of a mask holder, and form no part of the claimed design. 

CLAIM The ornamental design for an mask holder, as shown and described. 